In recent past development of silver nanoparticles and their application in the treatment of wastewaters is becoming a major area of research. It is mainly applicable to the removal of three major pollutants like pesticides, heavy metals, and microorganisms. Variety of synthesis techniques have been reported for preparation and characterization of silver nanoparticles. In our research, we synthesized Ag nanoparticles supported on ZrO2 and ZrO2-CeO2 by a “deposit-precipitation method” as the first step and later sequentially synthesized Ag-Au supported on ZrO2 and ZrO2-CeO2 by Redox method. Catalysts were evaluated in catalytic wet air oxidation (CWAO) of methyl tert-butyl ether and phenol. The CWAO is a liquid phase process for the treatment of organic pollutants operating at temperatures in the range of 100–325°C at 5–200 bar pressures. The selectivity and efficient of catalysts were evaluated by total organic carbon (TOC) and high-performance liquid chromatograph (HPLC). Ideally, the total mineralization of pollutants into CO2 and H2O is preferred.
Part of the book: Silver Nanoparticles
Rare earth doping ions can improve the spectral response of this semiconductor to the visible region. This work evaluated the dopant effect of rare earth ions such as La, Ce, Nd, Pr, Sm, Eu, and Gd in titania for the solar photodegradation of Diuron and methyl parathion. The increase in the content up to 0.5% of dopants decreases photoactivity due to the formation of photo-generated electron-hole pair recombination centers. The catalysts calcined at 500°C presented only the anatase crystalline phase and the samples doped with La and Ce at 0.1 and 0.3% were the most active in diuron solar degradation; however, when the temperature of the thermal treatment increased to 800°C, mixtures of crystalline phases were presented. The catalyst with the highest anatase content showed the best performance. The materials calcined at 500°C with better performance in diuron solar degradation were selected to to treat methyl parathion using solar light. Finally, under these conditions, an affinity was found for the dopant ions in titania and in the functional groups of the contaminating molecules (phenylurea and thiophosphate). Solar photodegradation of diuron was more effective with La and Ce, while for methyl parathion, it was Eu at 0.3%.
Part of the book: Water and Wastewater Treatment